A crop sprayer is used to distribute chemicals, such as herbicides, pesticides, and fertilizer, over crops in a field during a spraying operation. In order to maneuver the crop sprayer around the field during the spraying operation, an operator of the crop sprayer operates various controls which affect speed and direction of the crop sprayer. Note that speed and direction of the crop sprayer is directly related to the rotational speed and direction of a drive shaft of the crop sprayer.
One of the above controls allows the operator to selectively couple and decouple an engine crankshaft of the crop sprayer from the drive shaft. Another of the above controls allows the operator to selectively change the gear ratio between the engine crankshaft and the drive shaft. Still another of the above controls allows the operator to selectively increase and decrease rotational speed of the engine crankshaft.
To control the movement of a conventional tractor, a foot activated clutch is used to selectively couple and decouple the engine crankshaft from the drive shaft, a hand actuated gear selector is used to selectively change the gear ratio between the engine crankshaft and the drive shaft, and a foot actuated throttle is used to control the rotational speed of the engine crankshaft.
In addition to the controls which the operator must operate in order to maneuver the crop sprayer around the field, the crop sprayer also includes other controls which operate the chemical spraying features of the crop sprayer. In particular, the crop sprayer has a boom arm control which raises, lowers, extends, and retracts a boom arm. The crop sprayer further has a spray control which adjusts the flow rate of chemicals from a storage tank through a number of nozzles mounted on the boom arm.
As can be seen from the above, there exists a significant number of separate controls which an operator must manipulate to control the movement and chemical spraying features of the crop sprayer. Manipulation of this significant number of controls may create a burden on the operator.
One manner of reducing the above burden on the operator of the crop sprayer is to utilize a hydrostatic drive system in the crop sprayer. The hydrostatic drive system includes a hand lever which when manipulated causes a hydraulic fluid to be advanced within the system so as to cause rotation of the wheels of the crop sprayer at a desired rotational speed and direction. Thus, use of the hydrostatic drive system eliminates the need for an operator to (i) use his foot to activate a clutch to selectively couple and decouple the engine crankshaft from the drive shaft, and (ii) to use his foot to selectively actuate the throttle to control the speed of the engine crankshaft. A separate control may be used to selectively change the gear ratio between the engine crankshaft and the drive shaft. Consequently, use of a hydrostatic drive system enables an operator to maneuver the crop sprayer around the field with a fewer number of separate controls thereby reducing the burden on the operator of the crop sprayer.
However, a drawback to using a hydrostatic drive system is that the hydrostatic drive system is typically heavy, complex, and expensive. The weight of the hydrostatic drive system inhibits mobility of the crop sprayer, especially in soft terrain. Wider tires can be used to distribute the weight of the crop sprayer over a larger area so as to increase mobility. However, the use of wider tires would require an additional distance to be provided between rows of the crop in order to enable clearance for the wider tires. Alternatively, if the additional distance between the rows of the crop is not provided, the wider tires would tend to tread on the crops thereby damaging a portion of the crop during a spraying operation. In either case, crop production is reduced by using wider tires.
What is needed therefore is an apparatus and method for reducing the number of separate controls required to control the movement and operate the spraying features of a crop sprayer without significantly increasing the weight of the crop sprayer.